AC68U Mediabridge + USB 3 = Problem

[Onemangang]

Hi everyone.

A week ago I bought 2 x RT-AC68U, and it felt like christmas
But after a week of fiddeling around i am at a complete loss of what to do.

My problem is this:

The first router is set up normally, with a ssid on each band, Asus/Asus_5G.
The second router is connected as mediabridge to the first on the 5G band.

Both routers have clients on the lan ports in gigabit mode, and router one
also services our phones, laptops and tablets on wireless 2.4GHz G+N.

Copying files between computers over the mediabridge gives me speeds
around 50MB/sec at a link speed of 702Mbit/sec. That is quite ok.

The first router also has a usb3 drive attached to it's usb3 port.
This is where the trouble starts for wireless 5G.

If i try to read any data from that usb3 drive over the media bridge,
i get at best 3MB/sec, yes 3 megabyte, and the copy seems sluggish.
Writing to it can sometimes be a little faster for some reason.

If I read data from it on one of my computers directly attached to the
gigabit ports, I can get up to around 52MB/sec, it varies a little.

But any traffic on the 5G band is a no go, as long as the usb3 disk
is working.

My laptops (2.4GHz/N) will all read from/write to that usb3 disk with
around 13MB/sec. Plugging the same usb3 disk in a computer gives
speeds of around 105-108MB/sec. So the drive is working.

So basically the usb3 port kills my 5G, wich is pretty much the opposite of
what i have read about interferrence on the 2.4GHz band and usb3.

Also, setting the "interferrence" setting back to activated does'nt do
anything for me. I have to dismount the usb3 drive and do a full reset
with the resessed button on the back to get it back to running in usb2
mode again.

I spoke with asus support in Sweden ( I live in Denmark ) and they where
pussled. They suggested to get my money back, for surely those two
devices are buggy. But what are the changes for that heh?

I then tried to switch the two routers to change roles, but i got the
exact same behavior, speed and everything.

I have also updated to the latest firmware on them both, and i even
tried Merlins .39 build today, still the same issue remains.

I really like those routers. Should i keep them and only use usb2 mode?
The usb3 port was the important factor for me, and now i cant use it.

On a side note:
I asked asus support if it was okay to try a custom firmware to try
and fix the problem, without voiding warranty. That was actually ok.
I would not void my warranty as long as any problems where not
caused by that firmware.

When both usb ports are in usb2 mode, i can read/write with around
28 MB/sec to the disk(s).

My usb3 drives are all Medion 2½ inch using the "asmt 2105" controller.
The cables are quite thick wich i guess means they are shielded ok.

Anyway, I still have a few days left before its too late to return them.
If anyone has any suggestions, I am all ears.

I'd really like to keep these routers, but that usb3 thing is a killer for me.

Regards

 

[Ford Prefect]

The first router also has a usb3 drive attached to it's usb3 port.
This is where the trouble starts for wireless 5G.

If i try to read any data from that usb3 drive over the media bridge,
i get at best 3MB/sec, yes 3 megabyte, and the copy seems sluggish.
Writing to it can sometimes be a little faster for some reason.

If I read data from it on one of my computers directly attached to the
gigabit ports, I can get up to around 52MB/sec, it varies a little.

But any traffic on the 5G band is a no go, as long as the usb3 disk
is working.

...I agree that the actual discussion is around USB3 devices causing disturbance on 2.4GHz band.
However, what you describe could also lead to the conclusion, that radiation emitted by your 5GHz device - when in high use - is causing disturbance of your USB3-disks.

Assuming these disks are not inside a metal case, I'd make a test and (double-)wrap them in tin-foil and do a test.
Also testing with another disk or Adatper/SD-card is an option to eliminate this possibility from the list.

Edit: exchanging USB3 cabling is another option, too.

 

[Onemangang]

Hi.

That was actually a brilliant thought.

I should have thought of that myself since i used to design
audio power amplifiers, where you have to take those things
into account too.

I'm gonna try test that shortly.

Thank you.
Will let you know if it makes a difference

 

[Onemangang]

Hi.

I testet my disk again, this time wrapped into several layers
of aluminium foil, and grounded. It didnt really make a difference.
It made me think of something else.

This time, while testing the usb3 speed over the mediabridge,
I started copying a huge file from one of the other computers over
the mediabridge at the same time. Surprisingly, that still worked
at 40+ MB/sec, while the usb transfer was still very slow.

Also...
Copying a huge file from the usb3 disk on the router to a wired client
gives good speed. Starting another transfer between computers across
the mediabridge at the same time, the transfer from usb3 to wired
client should slow dramatically down, but it does not.

That suggests that the devices are not interferring with each other.
The only thing that is slow is transfering from usb3 over media bridge.
(In usb2 mode the same disk gives full speed, around 28MB/sec)

Some more tests and info:

Transfer from the attached usb3 disk is around 40-52MB/sec with a
wired gigabit client directly to the router. (Speed varies a lot)

Transfer from the attached usb3 disk is around 2-3MB/sec over the
media bridge. (usb3 mode, wired -> mediabridge -> wired)

Transfer between computers over mediabridge, no usb3 activity,
is 40+ MB/sec ( often it reaches 50+ )

Transfers between computers over mediabridge, with usb3 file copy
to the same computer at the same time still comes to 40+ MB/sec.

So, usb3 to wired is quite fast, even when 5G is maxed out.

This doesnt make much sence to me...

I repeated thoses tests several times, while having "top" running
in telnet on the router with the usb3 disk.

This was quite interesting.
The cpu usage of the processes where quite different each time,
and very much following the throughput.

The "samba" process varies from around 5 up to 45%.
The "kworker" process varies from around 1 up to 15%.
The "usb-storage" varies from around 1 up to 12%.

Btw, on a side note, the filesystem on the usb3 disk is ntfs.

Looking at "top" while doing usb3 transfers over mediabridge shows
that it doesnt really use any noticeable cpu resources, so that is
not the problem.

I dont know a lot about linux's inner workings in detail, although i
am not a newbie in using it. I was wondering, if the usb3 handling and
the wireless 5G maybe share some interrupt like soundcards on the pc
back in the day....

In any case, I am even more confused then when i started testing.

Regards and thank you for reading.

 

[Ford Prefect]

Also...
Copying a huge file from the usb3 disk on the router to a wired client
gives good speed. Starting another transfer between computers across
the mediabridge at the same time, the transfer from usb3 to wired
client should slow dramatically down, but it does not.

That suggests that the devices are not interferring with each other.
The only thing that is slow is transfering from usb3 over media bridge.
(In usb2 mode the same disk gives full speed, around 28MB/sec)

Yes, that was my first tought on the cause that might bug you.
Now you have proof that this is not the case...unfortunately, I'd say.

I dont know a lot about linux's inner workings in detail, although i
am not a newbie in using it. I was wondering, if the usb3 handling and
the wireless 5G maybe share some interrupt like soundcards on the pc
back in the day....

In any case, I am even more confused then when i started testing.

As an USB2 disk is working fine, I doubt that a linux process, that only sees the filesystem or a remote protocol, affecting SAMBA, could be the cause.

The only thing uncommon is the device-type, USB3 vs. USB2 and thus the driver.
Since the USB3 device is working fine on wired and on 2.4GHz but not on 5GHz, what
could be uncommon to the system?
Yes, the thought of a hardware conflict comes to mind, but IMHO that should occur when hardware is in use and you proofed that this is not the case.
Why should it matter where the stream originates, from another 5G client or from USB3?
In what way is the network interface connected differently when traffic is routed through wired or wireless-2.4G/-5G respectively?
Is there some kind of "port-forwarding" in place that makes the traffic between 5G+USB3 getting routed though some extra loops (assuming the interface when on USB2-mode is named and treated differently and this is why USB2 works)?

 

[Onemangang]

Hi again.

All the tests are done with a complete reset to factory settings using the
button on the back.

Only thing i did was assigning a password to the two (differently named)
networks, and then enabling usb3 by disabling the interferrence flag.

The rest is untouched. So there should be nothing interfering with data
transfers.

Regards

 

[Ford Prefect]

...then it looks like everything "works as designed" or both units are indeed defective.
Very strange though.

 

[L&LD]

Has a different USB 3 cable been tested?

 

[Onemangang]

Has a different USB 3 cable been tested?

No, it hasnt. Unfortunatly i dont have any other types of usb3 cables.
But I doubt that is it. Like i said ealier, i can read from or write to the usb3
disk without problem from a wired client, while maxing out the wireless 5G
at the same time. Therefore i guess the cable is ok, as it seems the router
and the disk are not interferring with each other. The only time the tranfer
is slow is when i try to copy from usb3 disk over the media bridge.

Also, copying from the usb3 disk with a wired client, while copying from
the usb3 disk over the media bridge at the same time does not slow
the wired client down much. I still get 35-40MB/sec on wired client,
while wireless client gets max 3.

And i guess the reason for a little slowdown on the wired client is caused my the mechanical harddrive itself. It has to move its heads a lot read two files
at the same time. I guess you could say the slowndown is similar to reading
from a fragmentet disk versus a defragmented one.

Regards

Ps.

Are there any threads about usb benchmarks for the different routers?
Like the Netgear R6300V2/R7000 or Linksys EA6900....
I think that is actually missing.

I'm gonna try get another type of cable on my way home from work tommorrow and post my findings. Also, could it
be possible, that the problem only appears on wireless AC
because the disk and the router pulse signals at the same time? Could that be possible?

 

[Onemangang]

Hi again.

I have now bought a different cable that supposedly is shielded.
I get the exact same results.

So i guess the routers are going back to the store

Thank you all for your time and answers

Regards.

 

[L&LD]

The routers don't seem to be working as you want. But my solution would be to get a different USB3.0 HDD (as you tried both routers with it and they behaved the same) to try as well.

There is some interaction with this specific HDD enclosure that is giving you issues. The networking part; the routers seem to be doing perfectly though?


Just saying that there are two sides to every puzzle. I feel you're blaming the wrong part that doesn't fit.

 

[Onemangang]

Hi.

I don't think it is the drive itself, casing for it, or the cable.
It doesnt make sence. I did test ealier today with another cable,
(different brand) and got the same results.

If we summarize it all, all points to the routers, because:

1.
I can max out the usb3 to a wired client, while maxing out
the 5G network over the media bridge at the same time
between computers. This suggest they dont interfere
with each other.

2.
I can max out the 5G network by transferering data over the media bridge
between two computers, while also transfering from the usb3 disk
over the media bridge at the same time. The 5G network speed is not
affected when the usb3 transfer is startet.

So the only time the transfer to/from the usb3 disk is slow is when it passes
the 5G/AC network.

I actually tried something some minute ago.
I reconnected the mediabridge to use the 2.4GHz band instead.

And the disk delivers 22 - 24MB/sec sustained over the mediabridge
wich now runs in N mode. Linkspeed is 364.5Mbit.

Disk is still running in usb3 mode, interferrence flag is still off.

This also kinda proves, that the disk is'nt sending tons of noise out.
If it did, I would have lots of attenuation on the 2.4GHz band, but i dont.

As a final test, i set the disk back to usb2 mode, disabled the 5G radio
and reran the speed test. I got some funny numbers...

Now reading from the disk is slower then before, about 17MB/sec.
But writing to it maxes it out at 28MB/sec.
Link speed is steady at 405Mbps while copying in this way/mode.

I guess the little increase in linkspeed is because there is now only
one frequency on the antennas.

Anyway.
I love the design and the specs on those routers, But its decided.
They are going back.

Regards.

 

[L&LD]

Okay, color me confused.

You got it working and you're still returning it?

Hmmm

 

[Onemangang]

You got it working and you're still returning it?

Hi and thank you for replying.

No, it is'nt working.

What i am saying is, that if I only use the 2.4GHz band, everything
seems to work stable, including the disk in usb3 mode, but it's running
N only, no AC.

Using the 5GHz band (AC) makes usb disk transfer over the
mediabridge very slow, but anything else is blazing fast.

I bought these routers because they are about as fast as they get.
But only being able to utilize half their speed simply is not ok.

The whole point was to have a AC media bridge to use for streaming,
fileserver, backup... This way i could get rid of a old power hungry
computer that runs as server, and gain ultra fast wireless networking.

But i can't use usb3 mode when running AC wireless.

Edit, L&LD:

You are offcause correct that there are two sides to every puzzle
But if you read all the tests I've done, I don't think there can be any
other conclusion.

Regards

 

[L&LD]

I have read what you wrote but I can't seem to grasp it, I guess.

With the media bridge, you do realize that your throughput is halved, right?

I think a diagram might help (me at least!) see how you had it setup (because I believe you'll run into the same problems no matter which hardware you get).

 

[Onemangang]

Hi, I will gladly make a diagram for you as soon as i can.

it will be a series of Pictures wich i hope i can attach.

Regards

 

[JEWBSV]

I have exactly the same situation. AC68U two, one of them operates in mediamost. Speed ​​when copying a file AC68 (USB3.0)-AC68 (bridge) 5Hz, not more than 22 MB / s. Cables changed, the result is zero. If you interrupt and immediately start the copy, sometimes shows speed 47mb / s, but then the speed drops. Maybe the contrary, speed vozrastaest 2-3 to 20 MB / s

HDD (Backup Plus Desktop 3TB Drive
STCA3000101) Format EXT4
http://www.seagate.com/external-hard-drives/desktop-hard-drives/backup-plus-desk-v1/#specs

 

[Onemangang]

Hi.

This is a simple drawing of the setup i had.

Sorry about the symbols, had to use a simple
freeware schematic program to make this.

Router 1 is the main router.

Router 2 is connected to router 1 as media bridge,
wich essentially gives us a wireless networking switch.

Both routers have two wired clients that are all gigabit
capable. On each side of the mediabridge, one of the
computers has a ssd disk that has a share.
They can read and write *very* fast.

Transfers between computer 1 and computer 2 is always 80MB++/s
Transfers between computer 3 and computer 4 is always 80MB++/s

Transfers between computer 1 or 2 to computer 3 or 4 over the
mediabridge is always 45MB++/s in AC mode ( ~28MB/s in N ).
Usually it peaks at about 52-53MB/s.

Transfers between computer 1 or 2 and the USB3 disk is maxing
out router 1 at around 52MB/s both ways. (read or write)

Transfers between computer 3 or 4 and the USB3 disk is slow,
with speeds of around 2.8 - 3.0MB/s

Transfers between computer 1 or 2 to computer 3 or 4,
while also transferring from USB3 disk to same target still
is always 45MB++/s, where 2.8 - 3.0MB/s is the USB3 disk.

Transferring like above, but to different target computers
gives the exact same result.

So the AC network deliver its full potential here, regardless
if the USB port is set to USB2 or USB3 mode (interferrence flag).

I think the above proves that it's not the disk, cable or any
sort of interferrence.

-----------------------------------------------
Switching to 2.4GHz N, disabling the 5G radios:
-----------------------------------------------

Now *everything* works as expected, even the USB3 disk over
mediabridge, while in USB3 Mode (interferrence flag off).

Downside is that i only get around half the AC speed over the
mediabridge. It now peaks at 30MB/s with typically 28MB/s sustained.

Thats why i return the routers.

Edit:
I uploaded a better picture, somehow the first one got too big
Also a few spelling errors where corrected.
(English is not my native tounge)

Regards.

 

[L&LD]

Thanks for taking the time to document this.

After having read it a few times, I still think it is the USB disk that is the issue (it interferes with the 5GHz band).

If you still had this setup, I would suggest using a USB Hub to see if the issue persists. Or better yet; another make/model (chipset, specifically) USB 3.0 drive.

To me; the fact that it works when the media bridge is on the 2.4GHz band is the clue that the 5GHz band is interfering with the HDD.

Another set of routers (with better shielding on the USB 3.0 port) may indeed give better performance as you would expect, but it may also do exactly the same thing (if the issue is with the USB 3.0 HDD or cables used).

 

[Onemangang]

Hi.

I dont see anymore how it could be the disk,
since I can have it on full speed at the same
time as using 5G networking to its full potential.

There is no interferrence, otherwise the speeds
I get would be much lower.

Some extra information:

I get the same AC speed when the disk is not
connected at all. Connecting it doesnt slow down
the AC connection. The disk just runs a *LOT*
slower in AC mode then in N mode.

Regards.